--force- things, --no-force- things, --refuse- things
Force or refuse (no-force and refuse mean the same thing) to do some things. things is a comma separated list of things specified below. --force-help displays a message describing them. Things marked with (*) are forced by default.
Warning: These options are mostly intended to be used by experts only. Using them without fully understanding their effects may break your whole system.
all: Turns on (or off) all force options.
downgrade(*): Install a package, even if newer version of it is already installed.
Warning: At present dpkg does not do any dependency checking on downgrades and therefore will not warn you if the downgrade breaks the dependency of some other package. This can have serious side effects, downgrading essential system components can even make your whole system unusable. Use with care.
configure-any: Configure also any unpacked but unconfigured packages on which the current package depends.
hold: Process packages even when marked "hold".
remove-reinstreq: Remove a package, even if it's broken and marked to require reinstallation. This may, for example, cause parts of the package to remain on the system, which will then be forgotten by dpkg.
remove-essential: Remove, even if the package is considered essential. Essential packages contain mostly very basic Unix commands. Removing them might cause the whole system to stop working, so use with caution.
depends: Turn all dependency problems into warnings.
depends-version: Don't care about versions when checking dependencies.
breaks: Install, even if this would break another package.
conflicts: Install, even if it conflicts with another package. This is dangerous, for it will usually cause overwriting of some files.
confmiss: Always install a missing conffile. This is dangerous, since it means not preserving a change (removing) made to the file.
confnew: If a conffile has been modified always install the new version without prompting, unless the --force-confdef is also specified, in which case the default action is preferred.
confold: If a conffile has been modified always keep the old version without prompting, unless the --force-confdef is also specified, in which case the default action is preferred.
confdef: If a conffile has been modified always choose the default action. If there is no default action it will stop to ask the user unless --force-confnew or --force-confold is also been given, in which case it will use that to decide the final action.
overwrite: Overwrite one package's file with another's file.
overwrite-dir Overwrite one package's directory with another's file.
overwrite-diverted: Overwrite a diverted file with an undiverted version.
architecture: Process even packages with the wrong architecture.
bad-path: PATH is missing important programs, so problems are likely.
not-root: Try to (de)install things even when not root.
bad-verify: Install a package even if it fails authenticity check.
--ignore-depends=package,...
Ignore dependency-checking for specified packages (actually, checking is performed, but only warnings about conflicts are given, nothing else).
--new, --old
Select new or old binary package format. This is a dpkg-deb(1) option.
--nocheck
Don't read or check contents of control file while building a package. This is a dpkg-deb(1) option.
--no-act, --dry-run, --simulate
Do everything which is supposed to be done, but don't write any changes. This is used to see what would happen with the specified action, without actually modifying anything.
Be sure to give --no-act before the action-parameter, or you might end up with undesirable results. (e.g. dpkg --purge foo --no-act will first purge package foo and then try to purge package --no-act, even though you probably expected it to actually do nothing)